This particular breakthrough involves going beyond a normal fiber optic network which would usually see millions or billions of photons sent. In other words, a classical light pulse. When one kicks off with a billion photons, the number might drop to a million along the way, which is why repeaters are used to boost the light pulses. Quantum physics will operate on a different level – that of individual photons, and the experiment involves teleporting a photon in an unknown state of “superposition”.
To be able to transmit or teleport these photons across a distance of 100km is a breakthrough, since it would translate to upping the ante for a new way of data encryption that might end up as reality for real-world use in due time. However, there is still much more work that needs to be done before it heads in such a direction.